Workpiece end position detection device and workpiece end position detection method

Abstract

Provided is a workpiece end position detection device that can accurately detect the position of the end of a workpiece even in a case where the workpiece has a tilted portion. A workpiece end position detection device (100) has: a control section (11) that controls the position of a machining head (30) on which a gap sensor (31) is mounted so that the gap detected by the gap sensor (31) is constant while the machining head (30) is scanned along the surface of a workpiece; and a workpiece end detection section (13) that detects the position of the end of the workpiece based on the coordinate position of the machining head (30) when the amount of change in the gap between the gap sensor (31) and the workpiece becomes equal to or greater than a prescribed threshold value during execution of the control by the control section to make the gap constant.

Description

Technical Field

[0001] This invention relates to a workpiece end position detection device and a workpiece end position detection method. Background Technology

[0002] When a workpiece is mounted on the worktable of a machining machine, there is a possibility that the workpiece may shift from a predetermined position. Machining machines are known to be configured to perform appropriate machining on the workpiece by detecting this positional shift (e.g., Patent Document 1).

[0003] In addition, there are known processing machines that scan the surface of a workpiece using a gap sensor mounted on a laser processing head, thereby detecting holes or the like formed in the workpiece (for example, Patent Document 2).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-042774

[0007] Patent Document 2: Japanese Utility Model Application Publication No. 3-85184 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] To detect positional deviations of workpieces mounted on a machining machine, accurate detection of the workpiece end is required. However, in workpieces such as sheet metal, the periphery is sometimes tilted. It is desirable to be able to accurately detect the position of the workpiece end even in situations where a tilted portion exists on a workpiece that should be flat.

[0010] Methods for solving problems

[0011] One aspect of this disclosure is a workpiece end position detection device, comprising: a control unit that, while scanning a machining head equipped with a gap sensor along the surface of a workpiece, controls the position of the machining head to keep the gap detected by the gap sensor relative to the workpiece constant; and a workpiece end detection unit that, during the execution of the control based on the control unit to keep the gap constant, detects the position of the end of the workpiece based on the coordinate position of the machining head when the change in the gap between the gap sensor and the workpiece reaches or exceeds a predetermined threshold.

[0012] Another aspect of this disclosure is a workpiece end position detection method, in which a machining head equipped with a gap sensor scans along the surface of a workpiece while controlling the position of the machining head to keep the gap detected by the gap sensor and the workpiece constant. During the execution of the control to keep the gap constant, the position of the end of the workpiece is detected based on the coordinate position of the machining head when the change in the gap between the gap sensor and the workpiece is above a predetermined threshold.

[0013] Invention Effects

[0014] Based on the above structure, even when a workpiece that should be flat has a tilted portion, the position of the workpiece end can be accurately detected.

[0015] These objects, features, and advantages of the invention will become more apparent from the detailed description of typical embodiments of the invention shown in the accompanying drawings. Attached Figure Description

[0016] Figure 1 This is a diagram showing the machine structure of a workpiece end position detection device according to one embodiment.

[0017] Figure 2 This is a block diagram showing the structure of the control system for the workpiece end position detection device.

[0018] Figure 3 It is a functional block diagram that represents the functional structure formed within the control device.

[0019] Figure 4 It is a diagram used to illustrate the positional offset of a workpiece.

[0020] Figure 5 This diagram illustrates the process of detecting and processing the positional offset of a workpiece.

[0021] Figure 6 This is a flowchart representing the workpiece end inspection and processing.

[0022] Figure 7 This is a diagram showing the scanning state of the machining head in Example 1, which illustrates the workpiece end detection action.

[0023] Figure 8 This is a chart used to illustrate the changes in the workpiece end detection action in Example 1.

[0024] Figure 9 This is a diagram showing the scanning state of the machining head in Example 2, which illustrates the workpiece end detection action.

[0025] Figure 10 This is a chart used to illustrate the changes in the workpiece end detection action in Example 2.

[0026] Figure 11 This is a diagram showing the scanning state of the machining head in Example 3, which illustrates the workpiece end detection action.

[0027] Figure 12 This is a chart used to illustrate the changes in the workpiece end detection action in Example 3.

[0028] Figure 13 This is a diagram showing the scanning state of the machining head in Example 4-6, which illustrates the workpiece end detection action.

[0029] Figure 14 This is a chart used to illustrate the changes in the workpiece end detection action in Example 4.

[0030] Figure 15 This is a chart used to illustrate the changes in the workpiece end detection action in Example 5.

[0031] Figure 16 This is a chart used to illustrate the changes in the workpiece end detection action in Example 6.

[0032] Figure 17 This is a diagram showing the scanning state of the machining head during the workpiece warpage detection process.

[0033] Figure 18 It is a chart used to illustrate the changes in the workpiece warping detection process.

[0034] Figure 19 This diagram shows a state where the warped portion of the workpiece has been eliminated, and a machinable area has been defined.

[0035] Figure 20 This is a diagram showing the scanning state of the machining head during the workpiece end detection operation in the comparative example.

[0036] Figure 21 This is a diagram showing the state of contact between the machining head and the workpiece during the workpiece end inspection operation in the comparative example.

[0037] Figure 22 This is a graph showing the amount of backlash during the workpiece end inspection operation in the comparative example.

[0038] Figure 23 This diagram illustrates the first example of a workpiece end detection action based on the combined use of high-speed and low-speed scanning.

[0039] Figure 24 This is a diagram illustrating a second example of a workpiece end detection action based on the combined use of high-speed and low-speed scanning.

[0040] Figure 25This diagram illustrates the action of restoring the machining head in the second example of a workpiece end detection action based on the combined use of high-speed and low-speed scanning. Detailed Implementation

[0041] Next, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used to denote the same structural or functional parts. The scales of these drawings have been appropriately altered for ease of understanding. Furthermore, the embodiments shown in the drawings are examples for carrying out the invention, and the invention is not limited to the illustrated embodiments.

[0042] Figure 1 This is a diagram showing the machine structure of a workpiece end position detection device 100 according to one embodiment. (See diagram below.) Figure 1 As shown, the workpiece end position detection device 100 includes: a control unit (CNC) 10, a servo amplifier 20, X-axis, Y-axis, and Z-axis motors 50 driven by the servo amplifier 20, a machining head 30 for position control of the X, Y, and Z-axis positions relative to the workpiece W via the driving of the X, Y, and Z-axis motors, a gap sensor 31 mounted on the machining head 30, and a gap sensor circuit 40. That is, the workpiece end position detection device 100 is configured as a machining machine. Furthermore, it is assumed that the X and Y axes are horizontal and the Z-axis is vertical.

[0043] The control device 10 is a numerical control (CNC) device that generates instructions to drive the motors of the X, Y, and Z axes according to the machining program and sends them to the servo amplifier 20. The servo amplifier 20 is composed of motor circuits that control and drive the motors of each axis, and executes servo control for each axis motor 50 according to the instructions from the control device 10.

[0044] The processing head 30 is, for example, a laser processing head with a nozzle for irradiating a laser. Furthermore, the processing head 30 is not limited to such an example and includes various processing heads for performing various processes.

[0045] The gap sensor 31 is a sensor that measures the distance to the workpiece W. As an example, the gap sensor 31 is a capacitive sensor that senses the electrostatic capacitance between the sensor and the object being measured, and outputs a signal representing the measured electrostatic capacitance to the gap sensor circuit 40. The gap sensor circuit 40 outputs the distance d (i.e., the gap between the gap sensor and the workpiece) from the electrostatic capacitance detected by the gap sensor 31, based on the fact that the electrostatic capacitance between the plate electrodes is proportional to S / d (electrode area, d: distance between electrodes). Hereinafter, the distance between the gap sensor 31 and the workpiece will also be recorded as the gap quantity. Furthermore, in Figure 1 In the figure, the clearance is indicated by an arrow marked with the reference numeral G.

[0046] Furthermore, the gap sensor 31 is not limited to an electrostatic capacitive sensor; eddy current sensors and other types of sensors can also be used. As a general usage, the gap sensor 31 is used as... Figure 1 When positioned above the workpiece W as shown, the gap sensor 31 measures the distance relative to the gap sensor 31 located in front (at... Figure 1 The gap sensor 31 is used for the purpose of electrostatic capacitance between workpieces located vertically below, but it is also used in the lateral direction (in the middle). Figure 1 It also has a certain degree of sensitivity in the horizontal direction (the middle part).

[0047] Workpiece W is illustrated here as a rectangular workpiece as shown in the hypothetical diagram. However, the shape of the workpiece is not limited to this. Workpiece W is placed on a worktable (not shown), and the machining head is moved relative to workpiece W along the X, Y, and Z axes under the control of the control device 10, thereby performing machining on workpiece W.

[0048] Figure 2 It means having Figure 1 A block diagram of the control system structure of the workpiece end position detection device (machining machine) 100. The control device 10 generates instructions for each axis motor 50 according to the machining program and sends them to the servo amplifier (motor circuit) 20. The servo amplifier 20 executes servo control of each axis motor 50 according to the instructions from the control device 10, and performs position control of the machining head 30. The gap sensor 31 outputs a signal representing the measured electrostatic capacitance to the gap sensor circuit 40. The gap sensor circuit 40 provides the control device 10 with the gap amount calculated based on the output from the gap sensor 31.

[0049] With this structure, the control device 10 can control the X, Y, and Z axis positions of the machining head 30. Furthermore, the control device 10 can perform gap control based on the gap amount (maintaining a constant distance between the gap sensor 31 and the workpiece).

[0050] Figure 3 This is a functional block diagram representing the functional structure formed within the control device 10. For example... Figure 3 As shown, the control device 10 includes: a control unit 11 that controls the position of the machining head 30, which is equipped with a gap sensor 31, to scan along the surface of the workpiece W, so that the gap detected by the gap sensor 31 between the machining head 30 and the workpiece W is constant; a change acquisition unit 12 that acquires the change in the gap between the gap sensor 31 and the workpiece W; and a workpiece end detection unit 13 that detects the position of the end of the workpiece W based on the coordinate position of the machining head 30 when the change is above a predetermined threshold. The control device 10 may also include: a workpiece warping detection unit 14 that detects warped areas on the workpiece based on the change.

[0051] The change acquisition unit 12 can obtain the gap amount from the gap sensor circuit 40 and the position information of each axis motor 50 of the X, Y, and Z axes from the servo amplifier 20. The change acquisition unit 12 calculates the change amount using at least one of the gap amount and the position information of each axis motor.

[0052] In addition, the control device 10 may also have the structure of a general computer, which includes a CPU (processor), ROM, RAM, storage device, operation unit, display unit, input / output interface, network interface, etc. Figure 3 The functional blocks of the control device 10 shown can be implemented by the CPU (processor) of the control device 10 executing various software stored in the storage device, or they can be implemented by a structure based on hardware such as ASIC (Application Specific Integrated Circuit).

[0053] The workpiece being processed (in) Figure 4 Workpiece W1 is placed on a worktable (not shown). Figure 4 As shown, there is a situation where the workpiece W1 is offset from its reference position P0. In order to detect the position of the workpiece W1 that has been offset, the control device 10 performs a position offset detection process as follows. Figure 5 This diagram illustrates the process of position offset detection. (Refer to...) Figure 5 The process of position offset detection and processing is explained.

[0054] (a1) Detect the positions B1 and C1 of the two end faces on one side of the workpiece W1.

[0055] (a2) Next, detect the position A1 of one end face on the other side that is adjacent to the above side.

[0056] (a3) Detect workpiece W1 from positions A1, B1, and C1. Figure 4 The slopes in the front-back and left-right directions (i.e., the slopes relative to the reference position P0).

[0057] In the processes (a1) and (a2) described above, the positions A1, B1, and C1 are detected by the workpiece end detection function of the control device 10 (workpiece end detection unit 13). Using the values ​​obtained in this way that represent the positional offset of workpiece W1, the control device 10 can correct the workpiece position in the machining program and appropriately perform machining on workpiece W1.

[0058] The workpiece end detection function of the control device 10 will be described below. As for the control device 10, (b1) the machining head scans by making the gap control effective (controlling the relative height between the workpiece and the gap sensor to be constant), and (b2) it detects the workpiece end when the distance between the gap sensor and the workpiece changes drastically at the workpiece end.

[0059] To achieve this workpiece end detection function, the control device 10 executes... Figure 6 The workpiece end detection process shown is a workpiece end position detection method. Figure 6 This is a flowchart illustrating the workpiece end detection process executed under the control of the processor of the control device 10. First, the control device 10 (control unit 11) scans the machining head 30 along the surface of the workpiece while controlling the position of the machining head to keep the gap detected by the gap sensor 31 constant (step S1). Next, the control device 10 (change amount acquisition unit 12) acquires the change in the gap between the gap sensor 31 and the workpiece during the execution of the control (gap control) by the control unit 11 (step S2). In this specification, the change amount includes various values ​​related to gap control error, changes in the distance between the gap sensor 31 and the workpiece, the relative speed between the gap sensor 31 and the workpiece, and other changes in the distance between the gap sensor 31 and the workpiece.

[0060] Next, the control device 10 (workpiece end detection unit 13) detects the position of the end of the workpiece based on the coordinate position of the processing head 30 when the change amount is above a predetermined threshold (step S3). Through this workpiece end detection process, the position of the workpiece end can be reliably detected even in cases where the workpiece, which is normally flat, has a tilted portion at its periphery.

[0061] The following describes a specific example of the operation of detecting the workpiece end based on the change amount obtained by the change amount acquisition unit 12. The specific examples described in detail below include the following.

[0062] Example 1: Detection of error quantities based on gap control

[0063] Example 2: Z-axis position-based detection

[0064] Example 3: Z-axis velocity-based detection

[0065] Example 4: Detection based on the rate of increase of the gap

[0066] Example 5: Detection of Z-axis descent speed based on the increase rate of gap.

[0067] Example 6: Detection based on (gap increase rate - Z-axis descent rate) / XY-axis combined velocity

[0068] Reference Figure 7 and Figure 8 The workpiece end detection action (based on the detection of gap control error) in Example 1 will be explained. Figure 7 This is a diagram illustrating the state of the gap control in this example. In the gap control, the error amount Δ is eliminated when an error amount Δ occurs relative to the target gap value T. The error amount Δ can be detected based on the output of the gap sensor 31 in the gap control.

[0069] Here, the processing head 30 is along Figure 7 Scanning is performed in the direction of the middle arrow (X-axis direction). Furthermore, it is assumed here that the originally flat workpiece W has a portion that slopes upwards at its periphery, as shown in the figure. In the gap control in the direction of the arrow in the figure, the distance between the gap sensor 31 (machining head 30) and the workpiece W is maintained at the target value T. Therefore, as shown in the figure, the machining head 30 maintains the target value T at its distance from the workpiece W and moves along the surface of the workpiece W.

[0070] Furthermore, if the machining head 30 (gap sensor 31) reaches the workpiece end, the gap at the workpiece end increases sharply. Therefore, the following speed of the machining head 30 in the Z-axis direction is delayed, and the gap control error Δ increases. In addition, even if the following speed of the machining head 30 in the Z-axis direction is fast enough, the distance between the machining head 30 and the workpiece W will diverge in the X-axis direction due to the continuous scanning in the X-axis direction, and the gap control error Δ will increase.

[0071] Figure 8 Figure 81 is a graph showing the shift in the gap control amount (i.e., the shift in the gap control error amount) when the action in this example is performed. Figure 8 In the diagram, the horizontal axis represents time, and the vertical axis represents the clearance control amount (T+Δ). Here, a threshold M1 is applied to the clearance control amount, and the position where T+Δ is above (or exceeds) the threshold M1 (reference numeral L1) is detected as the workpiece end. That is, in this example, a threshold is applied to the clearance control error amount. The clearance control error amount Δ begins to increase sharply at the workpiece end; therefore, the position where T+Δ exceeds the threshold M1 (reference numeral L1) is detected as the workpiece end, thereby enabling reliable detection of the workpiece end.

[0072] Reference Figures 9-10 The workpiece end detection action (detection based on Z-axis position) in Example 2 will be explained. Figure 9 This diagram illustrates the state of gap control in this example. In this example, the position (X-axis position) where the Z-axis position of the machining head 30 is below (or less than) a certain threshold is detected as the workpiece end. As described above, if gap control is enabled and scanning is performed, the laser head descends significantly downwards beyond the workpiece end. In this example, this descent is captured as a change in the Z-axis position of the laser head.

[0073] Figure 10Figure 82 illustrates the change in the Z-axis position of the machining head 30 (gap sensor 31) during the operation of this example. Figure 10 In the diagram, the horizontal axis represents time, and the vertical axis represents the Z-axis position. For example... Figure 10 As shown in Figure 82, the position where the Z-axis position is lowered to the Z-axis threshold M2 (reference numeral L1) is set as the workpiece end. Figure 10 As shown, the Z-axis position drops sharply if it exceeds the workpiece end. Therefore, by setting the detection position as below (or less than) the Z-axis threshold M2, the workpiece end can be reliably detected. The action in this example is equivalent to capturing the descent in the Z-axis direction as a change and determining whether the change exceeds the threshold. Furthermore, in this case, if the workpiece is warped or tilted, the detection accuracy may decrease depending on the height of the workpiece end.

[0074] Reference Figures 11-12 The workpiece end detection action (based on Z-axis speed) in Example 3 will be explained. Figure 11 This is a diagram illustrating the state of clearance control in this example. In this example, the position where the Z-axis speed is above (or exceeds) a threshold is detected as the workpiece end. As described above, if clearance control is enabled during scanning, the machining head 30 descends significantly downwards at locations beyond the workpiece end. At this time, the Z-axis descent speed also increases. In this example, this increase in Z-axis speed is captured. Furthermore, in Figure 11 In the figure, the arrow marked with reference numeral 91 indicates the speed in the scanning direction (X-axis speed), and the arrow marked with reference numeral 92 indicates the speed in the Z-axis direction.

[0075] Figure 12 Figure 83 illustrates the shift of the Z-axis position of the machining head 30 during the action in this example. Figure 12 In the graph 83, the horizontal axis represents time, and the vertical axis represents the Z-axis position. The control device 10 (change acquisition unit 12) obtains the Z-axis velocity by performing time differentiation on the graph 83. The Z-axis velocity is expressed as the slope of the graph. Figure 12 As shown, the workpiece end detection unit 13 detects the position where the Z-axis speed is above (or exceeds) the threshold M3 (reference numeral L1) as the workpiece end. The Z-axis speed of the machining head 30 increases sharply from the position where the gap sensor 31 exceeds the workpiece end, therefore, the workpiece end can be reliably detected based on the Z-axis speed.

[0076] Reference Figures 13-14 The workpiece end detection action (based on the detection of the increase rate of the gap) in Example 4 will be explained. Figure 13This is a diagram illustrating the state of clearance control in this example. In this example, the workpiece end is detected when the clearance increase rate is above (or exceeds) a threshold. As mentioned above, if a scan is performed with clearance control active, the clearance control error (Δ) increases sharply beyond the workpiece end. In this example, the workpiece end is detected by capturing the rate of increase of this clearance (clearance control error Δ).

[0077] Figure 14 This graph illustrates the rate of increase of the gap in the action of this example. The horizontal axis represents time, and the vertical axis represents the gap amount (T+Δ). Curve 84 represents the time progression of the gap in the action of this example. The control device 10 (change acquisition unit 12) obtains the rate of increase of the gap by differentiating the gap over time. The rate of increase of the gap ((d(T+Δ) / dt)) is represented by the slope of graph 84. Figure 14 As shown, the position where the gap increases at a rate greater than or exceeding a threshold M4 (see attached figure, L1) is detected as the workpiece end. The gap increases sharply at the workpiece end, and therefore, the rate of increase of the gap also increases sharply at the workpiece end. Therefore, it is possible to detect the position where the gap increases at a rate greater than or exceeding the threshold as the position representing the workpiece end.

[0078] Reference Figure 15 The workpiece end detection action (based on the detection of the increase rate of the gap - the descent rate of the Z-axis) in Example 5 will be explained. Furthermore, the scanning of the machining head 30 in this example is as follows: Figure 13 That is how it is done. As described above, when scanning is performed while performing gap control, the gap error amount (Δ) increases sharply at the workpiece end, and the machining head 30 (gap sensor 31) performs Z-axis tracking accordingly. In this example, at this time, the speed at which the workpiece surface moves away is detected as observed by the machining head 30 (gap sensor 31) descending along the Z-axis direction through the Z-axis tracking action. Since the speed of the workpiece surface observed from the machining head 30 (gap sensor 31) can be detected, the change in the height of the workpiece surface can be captured independently of the gap control gain.

[0079] Figure 15 This graph illustrates the rate of change of the workpiece surface height during the operation in this example. The horizontal axis represents time, and the vertical axis represents the difference between the Z-axis position of the gap sensor and the gap control value (T+Δ) (Z-(T+Δ)). The rate at which the workpiece surface moves away from the gap sensor 31 is obtained as the slope (d(Z-(T+Δ)) / dt) of graph 85. The position (labeled L1) where the slope of graph 85 is greater than or exceeds the threshold M5 is detected as the workpiece end.

[0080] Reference Figure 16The workpiece end detection action ((gap increase rate - Z-axis descent rate) / XY-axis combined rate) in Example 6 will be explained. Furthermore, the scanning of the machining head 30 in this example is as follows: Figure 13 That is how it is done. In Example 5 above, the speed at which the slope of graph 85 is detected has the property that it increases if the speed (combined speed of the XY axes) in the scanning direction of the processing head 30 is large. Therefore, in order to be unaffected by the speed in the scanning direction, in this Example 6, the value obtained by dividing the speed at which the slope of graph 85 in Example 5 is detected by the speed in the scanning direction (combined speed of the XY axes) is used as the change quantity. This value is a dimensionless value representing a quantity close to the spatial shape of the workpiece. In addition, since this value is independent of the speed (XY speed) in the scanning direction, it is possible to obtain the advantage that the threshold does not need to be changed according to the speed (XY speed) in the scanning direction.

[0081] Figure 16 Chart 86 shows the distribution of this value along the X-axis. Figure 16 In the middle, the vertical axis and Figure 14 Similarly, (Z-(T+Δ)) is represented, with the horizontal axis indicating the position in the scanning direction (in this example, the position in the X-axis direction). The position (labeled L1) above (or exceeding) the threshold M86 in graph 86 is set as the workpiece end position.

[0082] (Workpiece warping detection function)

[0083] Next, the warping detection function of the workpiece warping detection unit 14 will be explained. If a warped portion of a workpiece is processed, particularly in areas with large warping, laser processing defects and dimensional defects may occur. The control device 10 (workpiece warping detection unit 14) uses the change amount acquired by the change amount acquisition unit 12 to detect the warped portion (warped portion) of the workpiece. As a result, the control device 10 can be set to exclude the warped portion from the processing target area.

[0084] Reference Figures 17-19 The specific action process will be explained. Here, the change is represented by the aforementioned "(increase rate of the gap + descent rate of the Z-axis) / combined speed of the X and Y axes" (hereinafter, for convenience, it is recorded as the measured value). Furthermore, Figure 17 This indicates the state of the operation in this action example. Figure 18 This indicates the shift in the measured value. The following describes the process.

[0085] (c1) While controlling the gap, the machining head 30 scans along the scanning direction. Figure 17 ).

[0086] (c2) Changes in the monitored measurements (Chart 87) Figure 18 ).

[0087] (c3) In the stage before detecting the workpiece end (position L1), regions where the curvature or slope of Figure 87 exceeds the threshold are detected as warped areas. Figure 18 In the example, the region C1 from the area enclosed by the dashed circle CA to the end of the workpiece is detected as a warped portion.

[0088] (c4) and continue to monitor graph 87 of the measured values, detecting the position (position L1) where the slope of graph 87 exceeds the specified threshold M7 as the workpiece end ( Figure 18 ).

[0089] Through the above process, warping around the workpiece can be detected on one side of the workpiece in the scanning direction. Next, (d1) the above process (c1-c4) is performed on all four sides of the workpiece, or (d2) the above process (c1-c4) is performed on two sides of the workpiece. Since warping is considered the same on each opposite side, the warped area can be determined on all four sides of the workpiece. In either (d1) or (d2), warping can also be detected at multiple locations on one side using the above process (c1-c4), allowing for a more detailed determination of the shape of the warping along the side direction.

[0090] The control device 10 can also display the location information of the determined warped region on the user interface screen of the control device 10. In this case, the warped region C1 relative to the workpiece W3 can also be displayed as... Figure 19 The image is illustrated. The user can correct the area of ​​the workpiece by avoiding warping. Alternatively, the control device 10 can be configured to automatically perform corrections to avoid warping in the workpiece area. For example, as shown... Figure 19 As shown, when region C1 is detected as a warped portion on workpiece W3, the control device 10 can remove region F1 (after region C1) from workpiece W3. Figure 18 The area that is more inner than position PA1 is set as the processable area.

[0091] Here, in order to understand the usefulness of the workpiece end detection action in this embodiment, as a comparative example, refer to... Figures 20-22 An example of a detection operation at the workpiece end, in which the output values ​​of the gap sensor (detection value 1) and the gap sensor at the workpiece end (detection value 2) are pre-stored in the control device, will be described. In a comparative example, such as... Figure 20 As shown, the height of the machining head 30 (gap sensor 31) relative to the workpiece W0 along the Z-axis is set to a specified value, and the machining head 30 is moved (scanned) while detecting the gap amount.

[0092] In this operation, when the machining head 30 (gap sensor 31) is located above the surface of the workpiece W0, a detection value 1 is detected as the output of the gap sensor 31. On the other hand, when the machining head 30 (gap sensor 31) reaches the end of the workpiece W0, a detection value 2 is detected as the output of the gap sensor 31, thus enabling the detection of the gap end. Figure 22 Figure 181 illustrates the shift in the output of the gap sensor 31 under this condition. In Figure 181, at the workpiece end position L10, the output of the gap sensor 31 reaches the detection value 2, and the workpiece end position L10 is detected by detecting this value.

[0093] However, here, as Figure 21 As shown, assume the workpiece W4 is a portion that slopes towards the periphery. In the comparative example scan, the Z-axis position of the machining head 30 is fixed; therefore, the degree of slope can be detected. Figure 22 The output values ​​are shown in Figures 181 and 182. Figure 182 shows an example of the shift in the output of the gap sensor 31 when the tilt angle is relatively shallow. In the case of Figure 182, as the machining head 30 approaches the end of the workpiece, the gap between it and the workpiece narrows, and the value in Figure 182 gradually decreases; then, if it passes the end of the workpiece, the value increases. In the case of Figure 182, if a fixed detection value 2 is used to detect the end of the workpiece, a detection value is obtained. Figure 22 The position L11 in the middle is used to detect the erroneous position as the end of the workpiece.

[0094] Furthermore, in cases of strong tilt, such as Figure 22 As shown in Figure 181, it is also possible that the machining head 30 will come into contact with the workpiece surface during a phase midway through its movement toward the workpiece end (see Figure 181). Figure 21 Regarding this point, according to the workpiece end detection operation of this embodiment, since gap control is performed, the workpiece end can be reliably avoided without being affected by the tilt of the workpiece.

[0095] The control device 10 may also have at least one of the following functions.

[0096] (1) Offset correction

[0097] (2) Combination of high-speed and low-speed movements

[0098] (3) Prevent leakage

[0099] (Offset Correction)

[0100] As described above, in this embodiment, since the structure of the workpiece end is detected by increasing the gap control amount, an error may occur between the actual workpiece end position and the detection position. The control device 10 (control unit 11) may also have a function to correct such an error (hereinafter, also referred to as offset correction). It can be considered that this error depends on the scanning speed, threshold, responsiveness of the gap sensor 31, etc. The control device 10 can set the error as described below.

[0101] Since the sensitivity of the gap sensor relative to any position needs to be determined in advance, it is difficult to calculate the error completely. Therefore, as an example, a calculation method is used to infer changes such as scanning speed and gap control gain based on the actual error under the condition of detection by the gap sensor at a certain threshold. In this case, the following calculation rules can also be adopted: (r1) with respect to scanning speed, the error is simply proportional to the scanning speed; (r2) with respect to gap control gain, if the tracking performance is increased, the error decreases. However, the application of (r1) and (r2) differs depending on what values ​​are used as the change. Therefore, in the cases of Examples 1 to 6 above, the following calculation methods can also be used respectively.

[0102] Examples 1-4: The error depends on the scan speed and the gap control gain. Regarding the scan speed, the dependence is the same (proportional) across Examples 1-4. However, regarding the gap control gain, the dependence differs across Examples 1-4. When the gap control gain increases, in Examples 1 and 4, the part that the gap control cannot fully follow is designated as the workpiece end; therefore, the followable distance increases, and the error increases accordingly. In Examples 2 and 3, following is performed through gap control, and the workpiece end is designated by increasing the followable position or speed; therefore, the error decreases.

[0103] Example 5: Depends on scan speed, but not on gap control gain.

[0104] Example 6: It does not depend on either scan speed or gap control gain.

[0105] (Combination of high-speed and low-speed movements)

[0106] It has the advantage that a faster scanning speed can shorten the cycle time, but it also has the property of increasing the error in detecting the position of the workpiece end. Therefore, the following actions are performed:

[0107] (e1) First, the approximate position of the workpiece end is detected by high-speed scanning.

[0108] (e2) Next, a low-speed scan is performed to detect the accurate position of the workpiece end.

[0109] This method combines the advantages of shorter cycle time and more accurate position detection. Two specific action examples are provided to illustrate this.

[0110] Figure 23 This diagram illustrates the scanning state in the first example of workpiece end detection based on a combination of high-speed and low-speed actions. In this example, the action is performed according to the following procedure.

[0111] (f1) First, the machining head 30 is high-speed scanned in the scanning direction H1 to detect the approximate position of the workpiece end. Here, the workpiece end position L22 is detected. Furthermore, any of the above-described Examples 1 to 6 can be used as the operation for detecting the workpiece end in this case.

[0112] (f2) Next, the machining head 30 scans at a low speed while performing gap control in the opposite scanning direction H2. Then, the detected gap amount is returned to the target value (T) position L21 and detected as the workpiece end position. Thus, the accurate workpiece end position can be detected.

[0113] Figure 24 This is a diagram showing the scanning state in the second example of workpiece end detection based on the combined use of high-speed and low-speed actions. In this example, the action is performed according to the following procedure.

[0114] (g1) First, the machining head 30 is high-speed scanned in the scanning direction H11 to detect the approximate position of the workpiece end. Here, the workpiece end position L32 is detected. Furthermore, any of the above-described Examples 1 to 6 can be used as the operation for detecting the workpiece end in this case.

[0115] (g2) Next, the machining head 30 is moved back a specified distance in the opposite direction H12, and the gap is restored to the original gap through gap control.

[0116] (g3) Next, the machining head 30 is scanned at low speed in the scanning direction H13 to detect the workpiece end. Here, the workpiece end position L31 is detected. Furthermore, any of the above-described Examples 1 to 6 can be used as the operation for detecting the workpiece end in this case.

[0117] In the above process (g2), if the processing head 30 is retracted, it can also be done as follows: Figure 25 As indicated by the middle arrow H12A, the machining head 30 temporarily retracts upwards, and then retracts a predetermined distance in the opposite direction of the scanning direction H11, restoring the original gap through gap control. This reliably avoids collisions between the machining head 30 and the workpiece W during retraction.

[0118] (Prevents leakage)

[0119] To prevent the gap sensor (machining head) from colliding with the worktable during gap control as it descends through the portion of the workpiece with a hole. The specific process is as follows.

[0120] (h1) While performing gap control, a high-speed scan is performed along the scanning direction.

[0121] (h2) Monitor the Z-axis position during scanning, and stop the descent of the machining head 30 when the Z-axis position reaches the preset lower limit value of the Z-axis.

[0122] As explained above, the workpiece end position detection function of this embodiment can accurately detect the position of the workpiece end even when there is a tilted part in a workpiece that should be flat.

[0123] The present invention has been described above using typical embodiments. However, those skilled in the art will understand that changes, omissions, and additions can be made to the above embodiments without departing from the scope of the present invention.

[0124] The structures described in the above embodiments can be applied to various industrial machines that perform various processes using a processing head equipped with a gap sensor.

[0125] Figure 3 The functional structure of the control device shown is illustrative, and not all of its functional blocks are necessary structural elements. For example, there may be a structure in which the workpiece end detection unit 13 and the workpiece warpage detection unit 14 each include the function of the change amount acquisition unit 12.

[0126] The program that performs the workpiece end detection processing and other various functions described in the above embodiments can be recorded in various computer-readable recording media (e.g., semiconductor memory such as ROM, EEPROM, flash memory, magnetic recording media, CD-ROM, DVD-ROM, etc.).

[0127] Explanation of reference numerals in the attached figures

[0128] 10. Control device

[0129] 11 Control Department

[0130] 12. Obtaining the change

[0131] 13. Workpiece end inspection unit

[0132] 14. Workpiece Warpage Detection Department

[0133] 20 Servo Amplifier

[0134] 30 processing heads

[0135] 31 Gap Sensor

[0136] 40 Gap Sensor Circuit

[0137] 50 motors per shaft

[0138] 100 Workpiece end position detection device.

Claims

1. A workpiece end position detection device, characterized in that, have: The control unit, while causing the machining head equipped with a gap sensor to scan along the surface of the workpiece, controls the position of the machining head to keep the gap between the machining head and the workpiece detected by the gap sensor constant; The workpiece end detection unit, during the execution of control based on the control unit to keep the interval constant, detects the position of the end of the workpiece based on the coordinate position of the processing head when the change in the interval between the gap sensor and the workpiece reaches or exceeds a predetermined threshold. The change is a quantity obtained based on the position information of the motor driving the processing head.

2. The workpiece end position detection device according to claim 1, characterized in that, The change is a measure of the change in the position of the machining head along an axis perpendicular to the surface of the workpiece.

3. A workpiece end position detection device, characterized in that, have: The control unit, while causing the machining head equipped with a gap sensor to scan along the surface of the workpiece, controls the position of the machining head to keep the gap between the machining head and the workpiece detected by the gap sensor constant; as well as The workpiece end detection unit, during the execution of control based on the control unit to keep the interval constant, detects the position of the end of the workpiece based on the coordinate position of the processing head when the change in the interval between the gap sensor and the workpiece reaches or exceeds a predetermined threshold. The change is obtained by time differentiation of the value representing the interval between the gap sensor and the workpiece, and is the speed of the machining head in an axis perpendicular to the surface of the workpiece.

4. A workpiece end position detection device, characterized in that, have: The control unit, while causing the machining head equipped with a gap sensor to scan along the surface of the workpiece, controls the position of the machining head to keep the gap between the machining head and the workpiece detected by the gap sensor constant; as well as The workpiece end detection unit, during the execution of control based on the control unit to keep the interval constant, detects the position of the end of the workpiece based on the coordinate position of the processing head when the change in the interval between the gap sensor and the workpiece reaches or exceeds a predetermined threshold. The change is the difference between the speed of the machining head in the axial direction perpendicular to the surface of the workpiece and the rate of increase of the interval when the control unit controls the interval with respect to the workpiece in a constant manner.

5. A workpiece end position detection device, characterized in that, have: The control unit, while causing the machining head equipped with a gap sensor to scan along the surface of the workpiece, controls the position of the machining head to keep the gap between the machining head and the workpiece detected by the gap sensor constant; as well as The workpiece end detection unit, during the execution of control based on the control unit to keep the interval constant, detects the position of the end of the workpiece based on the coordinate position of the processing head when the change in the interval between the gap sensor and the workpiece reaches or exceeds a predetermined threshold. The change is a value obtained by dividing the difference between the speed of the machining head in the axial direction perpendicular to the surface of the workpiece and the rate of increase of the interval when the control unit controls the interval with the workpiece in a constant manner by the speed of the machining head in the scanning direction of the machining head.

6. A workpiece end position detection device, characterized in that, have: The control unit, while causing the machining head equipped with a gap sensor to scan along the surface of the workpiece, controls the position of the machining head to keep the gap between the machining head and the workpiece detected by the gap sensor constant; The workpiece end detection unit detects the position of the end of the workpiece during the execution of the control based on the control unit to keep the interval constant, according to the coordinate position of the processing head when the change in the interval between the gap sensor and the workpiece reaches or exceeds a predetermined threshold. as well as The workpiece warpage detection unit detects warped areas on the workpiece based on the amount of change. The control unit sets the area on the workpiece that excludes the area with the warping as the machinable area.

7. A method for detecting the position of a workpiece end, characterized in that, include: While the machining head equipped with a gap sensor scans along the surface of the workpiece, the position of the machining head is controlled to keep the gap between the machining head and the workpiece detected by the gap sensor constant. During the execution of the control that keeps the interval constant, the change in the interval between the gap sensor and the workpiece is obtained; and The position of the end of the workpiece is detected based on the coordinate position of the processing head when the obtained change amount is above a predetermined threshold. The change is a quantity obtained based on the position information of the motor driving the processing head.

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